Method for producing N-vinylformamide

Abstract

A method for producing N-vinylformamide through a vapor-phase thermal decomposition reaction using an evaporator ( 10 ) for evaporating a raw material, a thermal decomposition reactor ( 20 ) for thermally decomposing a raw material gas generated by the evaporator ( 10 ) and a condenser ( 30 ) for condensing a thermally decomposed gas generated by the thermal decomposition reactor ( 20 ), wherein the evaporation of the raw material is started in the evaporator ( 10 ) while the temperature of a tube wall of a first connection tube ( 40 ) that connects the evaporator ( 10 ) to the thermal decomposition reactor ( 20 ) satisfies a requirement represented by formula (1): (temperature of tube wall (° C.))≥0.37×(pressure of evaporator (mmHg))+205.

The invention claimed is: 
     
       1. A method for producing N-vinylformamide by a vapor phase thermal decomposition reaction using an evaporator for evaporating a raw material, a thermal decomposition reactor for thermally decomposing a raw material gas generated by the evaporator, and a condenser for condensing a thermally decomposed gas obtained by the thermal decomposition reactor, wherein
 evaporation of the raw material in the evaporator is started in a state in which a temperature of a pipe wall of a first connecting pipe for connecting the evaporator with the thermal decomposition reactor satisfies the following Equation (1):
   temperature of pipe wall (° C.)≥0.37×pressure of evaporator (mmHg)+205  Equation (1):
 
 
 
     
     
       2. The method for producing N-vinylformamide according to  claim 1 , wherein evaporation of the raw material in the evaporator is started in a state in which a temperature of a pipe wall of a second connecting pipe for connecting the thermal decomposition reactor with the condenser satisfies Equation (1) above. 
     
     
       3. The method for producing N-vinylformamide according to claim wherein the raw material is a N-(α-substituted-ethyl)formamide. 
     
     
       4. The method for producing N-vinylformamide according to  claim 3 , wherein the N-(α-substituted-ethyl)formamide is a N-(α-alkoxyethyl)formamide. 
     
     
       5. The method for producing N-vinylformamide according to  claim 2 , wherein evaporation of the raw material in the evaporator is started in a state in which temperatures of pipe walls of the first connecting pipe and the second connecting pipe satisfy the following Equation (2):
   temperature of pipe wall (° C.)≥0.37×pressure of evaporator (mmHg)+210.  Equation (2):
 
 
     
     
       6. The method for producing N-vinylformamide according to  claim 1 , wherein a temperature of a pipe wall of the thermal decomposition reactor is higher than a temperature of a reaction gas passing through the thermal decomposition reactor. 
     
     
       7. The method for producing N-vinylformamide according to  claim 1 , wherein a temperature of a heating medium of the thermal decomposition reactor is higher than the temperature of the pipe wall of the first connecting pipe by 10° C. or more. 
     
     
       8. The method for producing N-vinylformamide according to  claim 2 , wherein temperatures of pipe walls of the first connecting pipe and the second connecting pipe are less than 600° C. 
     
     
       9. The method for producing N-vinylformamide according to  claim 4 , wherein a flow velocity of N-(α-alkoxyethyl)formamide gas is in a range of from 0.1 m/sec to 100 m/sec. 
     
     
       10. The method for producing N-vinylformamide according to  claim 1 , wherein a part of the first connecting pipe is inclined upward and is connected to a lower portion of the evaporator.